Web folding apparatus and method



United States Patent [72] Inventors James A. Murphy, Toronto, Ontario,

Canada, Charles A. Lee Knoxville, Tennessee; Eduards Spravniks, Weston,Ontario, Canada 21 Appl. No. 737,034

[22] Filed June 14,1968

Continuation-impart of Ser. No. 569,671,

Aug. 2, 1966, now Pat. No. 3,472,504.

[45] Patented Nov. 24, 1970 [73] Assignee International Paper CompanyNew York, New York a corporation of New York. by mesne assignments [54]WEB FOLDING APPARATUS AND METHOD 16 Claims, 19 Drawing Figs.

[52] US. Cl..... 270/40 [51] Int. Cl. B65h 45/22 [50] Field of Search270/40, 41, 86

[56] References Cited UNITED STATES PATENTS 2,642,279 6/1953 Teall270/40 3,199,861 8/1965 Presnell et al. 270/40 3,291,479 12/1966 Greineret al..... 270/40 3,330,553 7/1967 Couzens et al 270/40 PrimaryExaminer-Eugene R. Capozio Assistant Examiner-Paul V. WilliamsAttorney-Robert Graham Mc Clenahan ABSTRACT: An apparatus and method forinterfolding a succession of webs into a continuously moving stack ofwebs. In an illustrative embodiment, there is provided a plurality offolding devices which are effective to interfold successive pairs oftissue webs by turning over an edge portion of one of the webssubstantially simultaneously with an edge portion of a previously laiddown web. At least one of the edge portions being interfolded by eachdevice is maintained in a substantially flattened condition during theturning over thereof so that its cross section forms a substantiallystraight line The folding devices are ofidentical construction andinclude guide elements having spiral-shaped surfaces which are similarin several respects to the surfaces ofa propeller blade. These surfacesdirect the edge portions of the webs along gradually curving pathsduring the interfolding operation Patented Nov. 24, 1970 3,542,356

Sheet L of 5 l WEB FOLDING APPARATUS AND METHOD CROSS REFERENCES TORELATED APPLICATIONS BACKGROUND OF THE INVENTION Although the presentinvention is useful wherever a stack or package of interfolded webs isrequired. one particularly advantageous use is in the facial tissuefield. As more fully described in U.S. Pat. No. 3,285,599 granted Nov.I5, 1966, to Perry 0. Ph'earson, James A. Murphy and Cecil H. Watkins, acommercial consumer-size box of tissue illustratively may contain 360separate sheets of tissue in short lengths cut from a long stack. Infacial tissue operations of this type, the stack is built up by bringingtogether 360separate tissue webs from 360 separate supply rolls oftissue. As the webs are assembled in the stack, they are interfolded bya series of folding devices to produce one or more longitudinal folds oneach web. The assembled stack is cut off into convenient lengths whichare then packaged in wrappers or paperboard boxes of a size suitable foruse by the consumer.

a Heretofore, difficulties have been encountered in the interfolding ofa succession of webs into a stack of webs. For example, in many ofthemachines previously employed for this purpose the individual foldingdevices included boards, rods, etc., having comparatively sharp foldingedges. These edges tended to form sharpbends in the webs with the resultthat unwanted creases and wrinkles appeared which occasionally renderedthe wrinkled portions of-the stack unsuitable for use. Anotherdifficulty has arisen because of the need, in many prior machines, formaking different types of folding devices depending upon whether it wasdesired to produce a left-hand fold or a right-hand fold in a given web.The prior folding devices were often of unnecessarily complicatedconstruction which resulted in a further increase in the already highcost of the machine.

SUMMARY One general object of this invention therefore, is to provide anew and improved apparatus and method for interfolding a succession ofwebs.

More specifically, it is an object of this invention to provide suchapparatus and method which avoids the unnecessary formation ofcreasesand wrinkles in the webs being folded.

Another object of this invention is to provide an apparatus and methodof the character indicated in which individual folding devices need notbe of different construction from one device to another.

Still another object of this invention is to provide a novel method forinterfolding a succession of webs in stacked relation.

A further object of the invention is to provide web folding apparatusutilizing comparatively simple mechanical elements which is economicalto manufacture and thoroughly reliable in operation.

In one illustrative embodiment of this invention, there is provided amachine and method for automatically interfolding a succession of websinto a continuously moving stack. The webs are directed in pairs fromsuitable supply rolls to a plurality of folding devices which aredisposed at spaced folding locations along the path of the stack. Thefolding devices include a first folding device for receiving a firstpair of webs to be interfolded into the stack, and a second foldingdevice for receiving a second pair of webs to be interfolded into thestack. The webs in each pair are led to the corresponding folding devicein contact with each other and in substantially unfolded condition, andthe webs in the first pair proceed along the path of the stack from thefirst folding device to the second folding device. Each of the foldingdevices is provided with guide elements having spiral-shaped surfacesfor turning over the edge portions ofthe webs and placing them so thatthe edge portion of one web lies between the edge portions of anotherweb. The thus interfolded stack is then cut to appropriate lengths forpackagingand delivery to the purchaser.

In accordance with one feature of several advantageous embodiments ofthe invention, at least one of the edge portions of the webs beinginterfolded by each folding device is maintained in a substantiallyflattened condition during the turning over thereof so that its crosssection forms a substantially straight line. With this arrangement, thehandling of the webs is maintained at a minimum, and the incidence ofunwanted creases or wrinkles is substantially reduced.

In accordance with another feature of the invention, in certainpreferred embodiments. the spiral-shaped surfaces on the guide elementsof the folding devices direct the edge portions of each of the receivedwebs along gradually curving paths, thereby further reducing thepossibility of producing unwanted creases or wrinkles in the webs.

In accordance with still another feature of the invention, in severalgood arrangements, the second folding device is effective to turn overthe edge portion of one of the received wet-s substantiallysimultaneously with the edge portion of a previously laid down web. Thearrangement is such that the webs in a given pair are interfolded into apreviously laid down pair prior to the completion of the folding of theprevious pair. As a result, the handling of the webs is further reduced,and a corresponding reduction is realized in the incidence of unwantedcreases and wrinkles.

BRIEF DESCRIPTION OF THE DRAWINGS tures thereof, will be understood moreclearly and fully from the following description of a preferredembodiment when read with reference to the accompanying drawings, inwhich:

FIG. 1 is a top plan view of successive pairs of facial tissue webs asthey are interfolded into a stack of webs in accordance with oneillustrative embodiment ofthe invention;

FIG. 2 is aside elevational view of the webs shown in FIG. 1, withportions of the folding devices therefor indicated in phantom lines;

FIGS. 3, 4 and 5 are vertical sectional views through the websrespectively taken along the lines 33, 4-4 and 5-5 in FIG. 2;

FIG. 6 is a side elevational view of one portion of a folding device forinterfolding the webs in the manner shown in FIGS. 1-5;

FIG. 7 is a side elevational view of another portion of the foldingdevice;

FIG. 8 is a side elevational view of the assembled folding deviceportions shown in FIGS. 6 and 7, together with certain additional parts;

FIG. 9 is a top plan view ofthe portion ofthe folding device shown inFIG. 6;

FIG. 10 is a top plan view of the portion of the folding device shown inFIG. 7

FIG. 11 is a top plan-view of the assembled folding device portionsshown in FIG. 8',

FIGS. 12-18 are vertical sectional views respectively taken along thelines 12-12 to 18-18 of FIG. 8, showing the progressive interfolding oftwo successive pairs FIG. 19 is a vertical sectional view through thepairs of webs shown in FIGS. 12-18 as the webs emerge from the foldingdevice of FIG. 8.

DESCRIPTION OF A PREFERRED EMBODIMENT f Referring to FIGS. l5 of thedrawings, there is shown a succession of facial tissue webs which arebeing interfolded into a continuously moving stack of webs indicatedgenerally at 25. The webs are led to the stack 25 from a series ofsupply rolls-(not shown herein but illustrated in the aforementionedU.S. Pat. application Ser. No. 569, 671) which are arranged in 3. pairsabove the path of the stack. As the webs are advanced in the stack,they-are interfolded by positioning an edge portion of one web betweenthe edge portions of another web. The assembled and interfoldedstack ofwebs is advanced along its path by a suitable conveyor mechanism and iscut off into finished lengths which are then packaged in wrappers orpaperboard boxes for the consumer.

The webs being interfolded into the stack 25 include a first pair ofwebs 26 and 27 and a second pair of webs 28 and 29. The webs 26 and 27in the first pair are received by a first folding device, the locationof which along the path of the stack is shown at 30, and the webs 28 and29 in the second pair are received by a second folding dev'ice locatedat 31. The webs in each pair are led to the corresponding folding devicewith the webs in contact with each other and in substantially unfoldedcondition. In addition to the webs 26 and 27, the first folding device30 receives a previously laid down pair of webs, one of which is visibleat 33. Similarly, in addition to the webs 28 and 29 the second foldingdevice 31 receives the webs 26 and 27 from the first folding device 30.

A plurality of folding devices, such as the devices 30 and 31, arearranged in spaced-apart relationship with each other at a series offolding locations along the path of the stack 25. As will become morefully apparent hereinafter, the folding devices are of identicalconstruction, and one device is provided for each pair of webs to beinterfolded into the stack. Each of the devices is effective tointerfold the webs by turning over a longitudinal edge portion of one ofthe received webs substantially simultaneously with an edge portion of apreviously laid down web. Thus, as best shown in FIGS. 3-5, the webs 26,27 and 33 respectively include left and right lon' gitudinal edgeportions 26a and 26b, 27a and 27b, and 33a and 33b. The webs 26 and 27are led to the folding'device 30 with their edge portions 26a and 27b inoverlapping contact with each other and with their edge portions 26b and27a on opposite sides of the device. The web 33 comprises one of a pairof webs which are similarly led to the immediately preceding foldingdevice (not shown). The web 33 is maintained substantially open as itpasses through the preceding device with its edge portions 33a and 33bin spaced apart relationship with each other. The edge portions 33a and33b remain in this relationship as the web moves through the spacebetween the preceding device and the device 30. The device 30 iseffective to simultaneously turn over the edge portion 33a of the web 33and the edge portion 26b of the web 26 so that the edge portion 26b liesbeneath the edge portion 33a. During the turning over of these edgeportions, each edge portion is directed along a continuously butgradually curving path. in addition, at least the edge portion 33a isheld in a substantially flattened condition throughout its passagethrough the folding devices, so that its cross section forms asubstantially straight line. The arrangement is such that the handlingof the webs is maintained at a minimum, with the result that unwantedcreases or wrinkles in the folded product are substantially reduced.

The edge portion 27a of the web 27 likewise is maintained in asubstantially flattened condition during its movement through thefolding devices 30 and 31. As the edge portion 27a passes through thedevice 30, it is raised with respect to the edge portion 27b. Theraising of the edge portion 27a continues in the space between thedevice 30 and the device 31, such that by the time the web 27 reachesthe device 31 its edge portions 27a and 27b meet at an acute angle. Thedevice 31 is effective to turn over the edge portion 27a substantiallysimultaneously with an edge portion'(not shown in FIGS. 3--5) of oneofthe webs in a subsequently laid down pair.

THEFOLDING DEVICES may be supported for movement in a direction oppositeto that of the stack 25 (FIG. 2) in a manner more fully disclosed incopending U.S. Pat. application Ser. No. 569,671 referred to heretofore.A sloping rectangular plate All is welded or otherwise suitably affixedto the lower end of the column 37. The plate 40 includes a pair ofinfeed rollers 41 adjacent the forward or leading end thereof (the leftend as viewed in FIG. 8) and a depending flange 42 along one side of theplate. The flange 42 is welded to one of the longitudinal edges of afolding element 43. As best shown in FIGS. 7 and T0, the element 43comprises a plate which is substantially flat but is twisted adjacentits forward portion to form a gradually curving folding surface 45. Thesurface 45 is shaped somewhat in the manner of a portion of a propellerblade or screw and is of generally spiral configuration. The rearwardlydirected portion of the element 43 forms a flattened channel or slot $6(FIGS. 13-18) with the adjacent portion ofthe plate 40.

Affixed to the folding element 43 immediately beneath the flange 42 is achannel member 48 (FIGS. I4ill6). The member 48 interconnects theelement 43 and a second folding element 50 disposed therebeneath. Theelement 50 is of generally V-shaped cross section and includes a flathorizontal portion SI and an upstanding portion 52. The portion 52 isbent such that at its forward or leading end it forms an angle ofapproximately 60 with respect to the horizontal portion 51. At therearward end, however, the portion 52 is substantially parallel to theportion 51. Intermediate the forward and rearward ends, the portion 52forms a gradually curving spiralshaped folding surface 54. This surfaceis somewhat similar to the folding surface 45 on the folding element 43but is of the opposite sense. That is, whereas the surface 45 isdisposed adjacent the right portion of the folding device 30, as seen inthe forwardmost sectional view of FIG. 12, and curves inwardly to theleft in the progressively rearward views of FIGS. 13 18, the surface 541is oriented adjacent the left portion of the device in FIG. 12 andcurves inwardly to the right in the succeeding FIGS. The surface 54 ispositioned at a level beneath the surface 45 adjacent the forwardportion of the folding device, but the comparatively steep downwardslope of the surface 45 is such that the surfaces are at the same levelfrom about the location of the section line l3-l3 (FIG. 8) to therearward end of the device.

As best shown in FIGS. 6 and 18, the rearward portion of the foldingelement 50 includes an upstanding tongue 56. The tongue 56 is formedfrom a separate piece 57 which is welded at 58 to the element 50. Thepiece 57 includes two flat sections 60 and 61 which define a horizontalopening 62 therebetween. The tongue 56 extends upwardly from the section60 and includes a slightly curved folding surface 63 on its inner sidewhich is disposed at an angle of approximately with respect to thehorizontal. The section 60 is coplanar with the adjacent portion 52 ofthe element 50 and is spaced therefrom to define a slot 65. As bestshown in FIG. 9, this slot extends at an angle with respect to thelongitudinal dimension of the folding device and is spaced a shortdistance ahead of the tongue 56. The forwardmost portion of the piece 57is bent outwardly to form a finger 67.

OPERATION The path of the various tissue webs through the folding device30 may be traced from an examination of FIGS. 12- 19. FIGS. l218illustrate the pair of webs 26 and 27, which are received by the device30 directly from the corresponding supply rolls, and also the previouslylaid-down pair of webs 33 and 34, which are received from theimmediately preceding folding device. FIG. 19 illustrates these fourwebs as they emerge from the device 30.

In the position shown in FIG. 12, the webs 33 and 34, having beenpreviously laid down on the stack 25, are disposed adjacent the lowerportion of the folding device 30 with the web 34 completely folded intothe stack but with the web 33 still in a comparatively open, unfoldedcondition. The edge portion 33b of the web 33 is positioned between thetwo edge portions 34a and 34b ofthe web 34, while the edge portion 33aof the flat plane. The orientation of the supply rolls is such that theinwardly directed edge'portion 26a of the web 26is positioned above andin overlapping relationship with the inwardly directed edge portion 27bof the web 27. The remaining edge portions 26b and 27a, on the otherhand, are located externally with respect to the device 30 on oppositesides thereof.

Upon reaching the position shown in FIG. 12, the web 27 remains in itsflattened condition, while the interfolding of the web 26 is initiatedby the folding surface 45 of the plate element 43. In this FIG 11s wellas in FIG. 13, the forward portion of the element 43 has been shown bydash lines. As the web 26 moves through the folding device 30 to therespective positions indicated in FIGS. 13-17, the surface 45 iseffective to turn over the edge portion 26b of the web 26 and toposition this edge portion beneath the edge portion 26a. The surface 45directs the edgeportion 26b along a continuously curving path until theportion 26b reaches the turned-over position shown in FIGS. 17-19. Inthis position the edge portion 26b lies between the edge portions 33aand 33b of the web 33; The change in direction of theedge portion 26b asit moves along its path is sufficiently gradual that the possibility ofproducing unwanted wrinkles or creases in the edge portion issubstantially eliminated. .The arrangement is such that the turning overof the edge portion 26b. takes place entirely during the passage of theweb 26 through the folding device 30.

Simultaneously with the turning overof the edge portion 26b of the web26, the edge portion 33a of the web 33 from the immediately precedingdevice is turned over by the folding device 30. The turning over of theedge portion 33a is initiated by the immediately preceding device in amanner to be described hereinafter with respect to the edge portion 270.The turning overof the edge portion 33a continues inthe space betweenthe two folding devices until by the time the web 33 enters the device30 and reaches the position shown in FIG. 12, the portion 33a meets theremaining portion 3312 at an angle which is. slightly less than 55. Theportion 33a is received by the folding surface 54 and is progressivelyfolded over the edge portion 26b as the webs continue their movementthrough the successive positions shown in FIGS. 13, 14 and 15.

As the web 33 approaches the FIG. 16 position, thefinger '67 engages theedge portion 330 immediately adjacent the longitudinal center line ofthe web. The finger 67 .directs the edge portion 33a into the angularlyextending slot 65. This slot is effective to urge the edge portion 33ato the right, as viewed in FIGS. 16 and 17, and thus insure that theedge portion is fully interfolded between the edge portions 26a and 26bof the web 26. At the time the web 33-reaches the position shown in FIG.18, the interfolding of the web is complete,'and the edge portion 33a isdisposed within the horizontal opening 62 between the folding elementsections 60 and 61. The remaining edge portion 33b of the web 33 isposed between the edge portions 340 and 34b ofthe web 34.

The edge portions 27a and 27b of the web 27 are maintained in asubstantially open condition as this latter web moves through thefolding device 30. The edge portion 27a moves around the rollers 41'(FIG. 2) and then traverses substantially the entire length of thefolding device without coming in contact therewithIAs the portion 27areaches the upstanding tongue 56 (FIG. 18), the portion contacts theinwardly facing surface 63 of the tongue and is guided by this surfacetoward the succeeding folding device. The surface 63 is effective toinitiate the turning over of the edge portion 27a, such that at the timethe web 27 leaves the device 30 the edge portion 27a meets theedge-portion 2711 at an angle ofapproximately 90. As best shown in FIG.19, the turning over of the edge portion 27a continues in the spacebetween the device 30 and the succeeding device. The edge portion 27a isreceived bythe folding surface 54 (FIG; 12) of the succeeding devicefective to simultaneously (1) completely turn over an edge portion ofone of the webs in the pair, thereby forming, say, a left-hand fold, (2)turn over an edge portionofa web received from the immediately precedingfolding device, thus completing a right-hand fold, and (3) initiate theturning over of an edge portion of the other web in the pair,preparatory to the formation of a right-hand fold. A portion of theright-hand fold for this latter web is formed in the space betweenadjacent folding devices and the fold is completed by the succeedingdevice. The arrangement is such that there is a total of not more thanone folding device for each pair of webs being interfolded by themachine.

It will be apparent from the foregoing description that each of the edgeportions being turned over by a given folding device is directed along acontinuously curving, spiral-shaped path, no sharp folding edges beingemployed. In addition, at least one ofthe edge portions, namely, theedge portion 27a, is maintained in a flattened condition throughout itsmovement through two successive folding devices so that the crosssection of the edge portion forms a substantially straight line. Withthis arrangement, the handling ofthe webs during the interfoldingoperation is maintained at a minimum, and a substantial reduction isrealized in the incidence of unwanted creases and wrinkles.

Each of the folding devices is of identical construction and isfabricated from only three separate pieces of sheet steel or other flatstructural material. The devices are of comparatively simpleconfiguration and are economical to manufacture in the large quantitiescustomarily employed in tissue folding machinery.

The terms and expressionswhich have been employed are used as terms ofdescription and not of limitation, and there is no intention, in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described, or portions thereof, it being recognizedthat various modifications are possible within the scope of theinvention claimed.

We claim:

1. In a machine for interfolding a succession of webs into acontinuously moving stack, in combination, a first folding devicepositioned along the path of said stack for receiving a first pair ofwebs, and a second folding device positioned along the path of saidstack in spaced relationship with said first folding device forreceiving a second pair of webs, said folding devices having guideelements for turning a given edge portion of one of said webs and agiven edge portion of another of said webs over said stack so that thelast-mentioned edge portion lies between the edge portions of said oneweb, said guide elements including plate means defining a graduallycurving surface for maintaining at least one of said given edge portionsin a flattened condition throughout the turning over thereof.

2. In a machine for interfolding a succession of webs into a stackofwebs, in combination, a first folding device positioned along the pathof said stack for receiving a first pair of webs to be interfolded intosaid stack, and a second folding device positioned along the path ofsaid stack immediately adjacent said first folding device for receivinga second pair of webs to be interfolded into said stack, said foldingdevices having guide elements for simultaneously turning a given edgeportion of one of said webs over said stack so that the last-mentionededge portion lies between the edge portions of said one web, said guideelements including plate means for maintaining'at least one of saidgiven edge portions in a flattened condition throughout the turning overthereof.

3. In a machine of the character set forth in claim 2, each of saidguide elements having a spiral-shaped surface for directing said givenedge portions along gradually curving paths during the turning overthereof.

4. In a machine for interfolding a succession of webs into acontinuously moving stack, in combination, a first folding devicepositioned along the path of said stack for receiving a first pair ofwebs to be interfolded into said stack, and a second folding devicepositioned along the path of said stack immediately adjacent said firstfolding device for receiving a second pair of webs to be interfoldedinto said stack, the webs in each of said pairs being led to thecorresponding folding device with the webs unfolded and in contact witheach other, said second folding device having guide elements forsimultaneously turning a given edge portion of one of said webs and agiven edge portion of another of said webs over said stack so that thelast-mentioned edge portion lies between the edge portions of said oneweb, one of said guide elements including means defining a graduallycurving surface for maintaining at least one of said given edge portionsin a flattened condition throughout the turning over thereof so that itscross section forms a substantially straight line.

5. In a machine for interfolding a succession of webs into acontinuously moving stack, in combination, a first folding devicepositioned along the path of said stack for receiving a first pair ofwebs to be interfolded into said stack, and a second folding devicepositioned along the path of said stack immediately adjacent said firstfolding device for receiving a second pair of webs to be interfoldedinto said stack, the webs in said first pair being directed from saidfirst folding device to said second folding device, said second foldingdevice having guide elements for turning a given edge portion of one ofthe webs in said first pair and a given edge portion of one of the websin said second over said stack so that the last-mentioned edge portionlies between the edge portions of the one web in said first pair, one ofsaid guide elements including means defining a gradually curving foldingsurface maintaining at least one of said given edge portions in aflattened condition throughout the turning over thereof so that itscross section forms a substantially straight line.

6. in a machine of the character set forth in claim 5, another of theguide elements for said second folding device having a curved foldingsurface for directing the other of said given edge portions along acurved path during the turning over thereof. 1

7. in a machine of the character set forth in claim 6, the degree ofcurvature for the folding surface on said one guide element being lessthan the degree of curvature for the folding surface on the other guideelement.

8. In a machine for interfolding a succession of webs into acontinuously moving stack, in combination, a plurality of substantiallyidentical folding devices positioned along the path of said stack inspaced-apart relationshipwith each other, said folding devices includinga first folding device for receiving a first pair ofwebs to beinterfolded into said stack and a second folding device immediatelyadjacent said first folding device for receiving a second pair of websto be interfolded into said stack, the webs in each of said pairs beingled to the corresponding folding device with the webs unfolded and incontact with each other, the webs in said first pair being directed fromsaid first folding device to said second folding device, said secondfolding device having guide elements for simultaneously turning a givenedge portion of one of the webs in said first pair and a given edgeportion of one of the webs in said second pair over said stack so thatthe last-mentioned edge portion lies between the edge portions of theone web in said first pair, one of said guide elements including platemeans for maintaining at least one of said-given edge portions in aflattened condition throughout the turning over thereof so that itscross section forms a substantially straight line.

9. In a machine of thecharacter set forth in claim 8, the guide elementsof said second folding device defining an elongated slot extending at anangle with respect to the path of said stack, said second folding deviceincluding finger means for directing said one given edge portion intosaid slot as it moves along said path.

10. In a method for interfolding a succession of webs into acontinuously moving stack as the webs move along a feed path the stepsof feeding a first pair of webs to a first folding location along saidfeed path, feeding a second pair of Webs to a second folding locationalong said feed path, turning a given edge portion of one of said websand a given edge portion of another of said webs over said stack at saidsecond folding location, inserting the last-mentioned edge portionbetween the edge portions of said one web at said second foldinglocation, and maintaining at least one of said given edge portions in aflattened condition throughout the turning over thereof so that itscross section forms a substantially straight line,

ii, In a method for interfolding a succession of webs in stackedrelation as the webs move along a feed path, the steps of feeding afirst pair of webs to a first folding location along said feed path,feeding a second pair of webs to a second ing location along said feedpath, directing said ct: webs along said feed path from said firstfolding location to said second folding location, simultaneously turninga given edge portion of one of said webs and a given edge portion ofanother of said webs over said stack at said second folding location,inserting the last-mentioned edge portion between the edge portions ofsaid one web at said second folding location, and maintaining at leastone of said given edge portions in a flattened condition throughout theturning over thereof so that its cross section forms a substantiallystraight line.

12. in a method for interfolding a succession of webs in stackedrelation as the webs move along a feed path, the steps of feeding afirst pair of webs in contact with each other in substantially unfoldedcondition to a first folding location along said feed path, feeding asecond pair of webs in contact with each other in substantially unfoldedcondition to a second folding location along said reed path, directingsaid first pair of webs along said feed path from said first foldinglocation to said second folding location, simultaneously turning a givenedge portion of one of the ebs in said first pair and a given edgeportion of one of the webs in said second pair over said stack at saidsecond folding location, inserting the lastmentioned edge portionbetween the edge portions of the one web in said first pair at saidsecond folding location, and maintaining at least one of said given edgeportions in a flattened condition throughout the turning over thereof sothat its cross section forms a substantially straight line.

13. In a machine for interfolding a plurality of webs into acontinuously moving stack, each of said webs having a longitu dinalcenter line and a pair of edge portions which extend in transverse crosssection continuously from said center line to the opposite edges of theweb, a folding device comprising a pair of guide elements positionedalong the path of said stack,

' each of said guide elements having a web-contacting surface whichgradually curves inwardly in the direction of movement of said stacktoward the longitudinal center thereof, the webcontacting surface on oneof said guide elements curving inwardly from adjacent one side of saidstack and the web con-' tacting surface on the other guide elementcurving inwardly from adjacent the opposite side of said stack, andmeans for feeding a pair of said webs through said folding device withthe webs in overlapping relationship with each other at the time theyreach said folding device, said feeding means directing a given edgeportion of one of the webs in said pair along the web-contacting surfaceof said one guide element and directing a given edge portion of theother web in said pair along the web-contacting surface of said otherguide element, said given edge portions being directed by said feedingmeans along the inwardly curving paths defined by said web-contactingsurfaces to gradually fold said given edge portions over said stack.

14. In a machine of the character set forth in claim 13, theweb-contacting surface of-said one guide element maintaining the givenedge portion therefor in a flattened condition during the turning overthereof so that its cross section forms a substantially straight line.

which the degree of curvature of the web-contacting surface of said oneguide element is less than the degree of curvature of the web-contactingsurface of the other guide element.

